1. Field Of The Invention
The present invention generally relates to a method and apparatus for comparing binary numbers, and more particularly relates to a method and apparatus for determining which of a plurality of binary numbers has the greatest value.
Even more specifically, the present invention relates to a method and apparatus for determining which binary number of a plurality of binary numbers has the greatest decimal value, and for minimizing any uncertainty associated with the determination.
2. Description Of The Prior Art
"Greatest of" or "GOF" circuits are well known in the art. A GOF circuit is oftentimes employed when it is necessary to determine which one or ones of a plurality of digital or analog signals has the greatest value.
For example, an analog GOF circuit can be embodied as a parallel arrangement of transistors having their emitters connected together. The base of each transistor receives one of a plurality of analog signals to be compared. The signal having the greatest amplitude will forward bias its corresponding transistor which, in turn, has the effect of back biasing the transistors connected to lower amplitude signals. The collector circuits of the transistors may be monitored to determine which transistor is turned on, indicating the signal of greatest amplitude.
One known technique for determining the greatest value of digitally coded signals, such as binary numbers, utilizes an iterative comparison method. In this method, one bit of each number at a time is compared sequentially with the corresponding bits of the other numbers being compared, usually starting with the most significant bit, the process being repeated with the second most significant bit, and so on, until a determination may be made.
A variation on the iterative method is one in which the first number of a set is subtracted from the second, the greater stored, compared against the third, continuing the process until the entire set has been tested.
Such iterative processes consume a significant amount of time, especially as the set of numbers being compared becomes large, or when each number being compared comprises a large number of bits.
Another digital technique for comparing binary numbers is commonly referred to as a "tree comparison" method. According to this process, pairs of binary numbers are compared in a first level of comparison. The largest numbers of the pairs are again compared in pairs in a second level of comparison. The method continues through various comparison levels until a comparison of the remaining pair of numbers yields the greatest number.
However, this technique proves inefficient in terms of its implementation and the physical devices it requires.